ST Elevation Differential Diagnosis
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Direct answer
ST elevation on an ECG is not always an infarction, and STEMI is the diagnosis that demands emergency reperfusion. Pericarditis, early repolarisation, LV aneurysm, Brugada pattern, hyperkalaemia and Takotsubo cardiomyopathy mimic it, and each is separated by the distribution, morphology and presence or absence of reciprocal change.
What you must remember
- Reciprocal change: ST depression in opposing leads supports STEMI, whereas pericarditis and early repolarisation usually lack it.
- Pericarditis: diffuse ST elevation in most leads with concave morphology and PR depression, usually sparing aVR.
- Early repolarisation: J-point notching or slurring with concave ST elevation in lateral leads, typical of young adults and athletes, and benign.
- LV aneurysm: persistent ST elevation with Q waves long after an anterior infarction, often with convex morphology.
- Brugada type 1: coved ST elevation of 2 mm or more in V1 and V2, followed by a negative T wave, with a risk of sudden cardiac death.
- Hyperkalaemia: tall, narrow, peaked T waves come first, and severe hyperkalaemia can produce ST elevation that mimics infarction.
- Takotsubo cardiomyopathy: ST elevation with apical ballooning across more than one coronary territory, often after emotional or physical stress, usually without a culprit occlusion.
- Sgarbossa criteria: used in left bundle branch block, where concordant ST elevation in leads with a positive QRS, or concordant ST depression in V1 to V3, suggests infarction.
A lead-by-lead comparison of mimics
The ECG pattern is judged by where the ST elevation lies, what shape it has, and whether opposite leads show depression. The table sets out those features for each condition.
| Condition | Distribution | Key clue |
|---|---|---|
| STEMI | Contiguous leads in one territory | Reciprocal depression, convex morphology |
| Pericarditis | Diffuse, most leads | PR depression, concave, no reciprocal change |
| Early repolarisation | Lateral or inferior leads | J-point notch, concave, benign |
| LV aneurysm | Territory of an old infarct | Persistent ST elevation with Q waves |
| Brugada type 1 | V1 and V2 | Coved ST elevation, negative T wave |
| Hyperkalaemia | Often V1 to V2, or diffuse | Peaked T waves, widened QRS |
| Takotsubo | Multiple territories | Apical ballooning, no culprit lesion |
Pericarditis and early repolarisation both look benign at first sight, so the clinical story and the PR segment decide between them. Hyperkalaemia and Brugada pattern are the mimics that change management immediately, through potassium correction and arrhythmia risk assessment.
Traps in ST elevation vignettes
Most ECG errors come from accepting the first ST elevation as infarction without checking its shape and distribution.
- Trap: calling diffuse ST elevation with PR depression a STEMI Correct: pericarditis gives diffuse, concave ST elevation without reciprocal depression, and pleuritic pain or a friction rub supports it.
- Trap: dismissing a Brugada type 1 pattern as benign because the patient looks well Correct: the pattern needs specialist assessment, particularly after syncope, a family history of sudden death, or fever, which can unmask it.
- Trap: treating hyperkalaemia on the ECG as an acute coronary event Correct: check potassium and treat it first, since the ECG changes often reverse once potassium falls.
Frequently asked questions
How does pericarditis differ from STEMI on the ECG?
Pericarditis gives diffuse, concave ST elevation in most leads, with PR depression and no reciprocal ST depression. STEMI gives ST elevation confined to contiguous leads of one coronary territory, usually with reciprocal depression and convex morphology.
What is the Brugada type 1 pattern?
The Brugada type 1 pattern shows coved ST elevation of 2 mm or more in V1 and V2, followed by a negative T wave. It carries a risk of sudden cardiac death in some patients, and fever or sodium channel blocking drugs can unmask it.
Can hyperkalaemia cause ST elevation that mimics infarction?
Yes, severe hyperkalaemia can cause ST elevation that mimics acute infarction, often with tall peaked T waves and a widened QRS. Potassium should be measured urgently, and the ECG changes usually reverse once potassium is lowered.
Why does Takotsubo cardiomyopathy mimic STEMI?
Takotsubo cardiomyopathy produces ST elevation and troponin release, both of which resemble an acute infarct. The wall motion abnormality spans more than one coronary territory, with apical ballooning and usually no culprit occlusion on angiography.